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      1 #!/usr/bin/env python3
      2 
      3 # Change the #! line occurring in Python scripts.  The new interpreter
      4 # pathname must be given with a -i option.
      5 #
      6 # Command line arguments are files or directories to be processed.
      7 # Directories are searched recursively for files whose name looks
      8 # like a python module.
      9 # Symbolic links are always ignored (except as explicit directory
     10 # arguments).
     11 # The original file is kept as a back-up (with a "~" attached to its name),
     12 # -n flag can be used to disable this.
     13 #
     14 # Undoubtedly you can do this using find and sed or perl, but this is
     15 # a nice example of Python code that recurses down a directory tree
     16 # and uses regular expressions.  Also note several subtleties like
     17 # preserving the file's mode and avoiding to even write a temp file
     18 # when no changes are needed for a file.
     19 #
     20 # NB: by changing only the function fixfile() you can turn this
     21 # into a program for a different change to Python programs...
     22 
     23 import sys
     24 import re
     25 import os
     26 from stat import *
     27 import getopt
     28 
     29 err = sys.stderr.write
     30 dbg = err
     31 rep = sys.stdout.write
     32 
     33 new_interpreter = None
     34 preserve_timestamps = False
     35 create_backup = True
     36 
     37 
     38 def main():
     39     global new_interpreter
     40     global preserve_timestamps
     41     global create_backup
     42     usage = ('usage: %s -i /interpreter -p -n file-or-directory ...\n' %
     43              sys.argv[0])
     44     try:
     45         opts, args = getopt.getopt(sys.argv[1:], 'i:pn')
     46     except getopt.error as msg:
     47         err(str(msg) + '\n')
     48         err(usage)
     49         sys.exit(2)
     50     for o, a in opts:
     51         if o == '-i':
     52             new_interpreter = a.encode()
     53         if o == '-p':
     54             preserve_timestamps = True
     55         if o == '-n':
     56             create_backup = False
     57     if not new_interpreter or not new_interpreter.startswith(b'/') or \
     58            not args:
     59         err('-i option or file-or-directory missing\n')
     60         err(usage)
     61         sys.exit(2)
     62     bad = 0
     63     for arg in args:
     64         if os.path.isdir(arg):
     65             if recursedown(arg): bad = 1
     66         elif os.path.islink(arg):
     67             err(arg + ': will not process symbolic links\n')
     68             bad = 1
     69         else:
     70             if fix(arg): bad = 1
     71     sys.exit(bad)
     72 
     73 ispythonprog = re.compile(r'^[a-zA-Z0-9_]+\.py$')
     74 def ispython(name):
     75     return bool(ispythonprog.match(name))
     76 
     77 def recursedown(dirname):
     78     dbg('recursedown(%r)\n' % (dirname,))
     79     bad = 0
     80     try:
     81         names = os.listdir(dirname)
     82     except OSError as msg:
     83         err('%s: cannot list directory: %r\n' % (dirname, msg))
     84         return 1
     85     names.sort()
     86     subdirs = []
     87     for name in names:
     88         if name in (os.curdir, os.pardir): continue
     89         fullname = os.path.join(dirname, name)
     90         if os.path.islink(fullname): pass
     91         elif os.path.isdir(fullname):
     92             subdirs.append(fullname)
     93         elif ispython(name):
     94             if fix(fullname): bad = 1
     95     for fullname in subdirs:
     96         if recursedown(fullname): bad = 1
     97     return bad
     98 
     99 def fix(filename):
    100 ##  dbg('fix(%r)\n' % (filename,))
    101     try:
    102         f = open(filename, 'rb')
    103     except IOError as msg:
    104         err('%s: cannot open: %r\n' % (filename, msg))
    105         return 1
    106     line = f.readline()
    107     fixed = fixline(line)
    108     if line == fixed:
    109         rep(filename+': no change\n')
    110         f.close()
    111         return
    112     head, tail = os.path.split(filename)
    113     tempname = os.path.join(head, '@' + tail)
    114     try:
    115         g = open(tempname, 'wb')
    116     except IOError as msg:
    117         f.close()
    118         err('%s: cannot create: %r\n' % (tempname, msg))
    119         return 1
    120     rep(filename + ': updating\n')
    121     g.write(fixed)
    122     BUFSIZE = 8*1024
    123     while 1:
    124         buf = f.read(BUFSIZE)
    125         if not buf: break
    126         g.write(buf)
    127     g.close()
    128     f.close()
    129 
    130     # Finishing touch -- move files
    131 
    132     mtime = None
    133     atime = None
    134     # First copy the file's mode to the temp file
    135     try:
    136         statbuf = os.stat(filename)
    137         mtime = statbuf.st_mtime
    138         atime = statbuf.st_atime
    139         os.chmod(tempname, statbuf[ST_MODE] & 0o7777)
    140     except OSError as msg:
    141         err('%s: warning: chmod failed (%r)\n' % (tempname, msg))
    142     # Then make a backup of the original file as filename~
    143     if create_backup:
    144         try:
    145             os.rename(filename, filename + '~')
    146         except OSError as msg:
    147             err('%s: warning: backup failed (%r)\n' % (filename, msg))
    148     else:
    149         try:
    150             os.remove(filename)
    151         except OSError as msg:
    152             err('%s: warning: removing failed (%r)\n' % (filename, msg))
    153     # Now move the temp file to the original file
    154     try:
    155         os.rename(tempname, filename)
    156     except OSError as msg:
    157         err('%s: rename failed (%r)\n' % (filename, msg))
    158         return 1
    159     if preserve_timestamps:
    160         if atime and mtime:
    161             try:
    162                 os.utime(filename, (atime, mtime))
    163             except OSError as msg:
    164                 err('%s: reset of timestamp failed (%r)\n' % (filename, msg))
    165                 return 1
    166     # Return success
    167     return 0
    168 
    169 def fixline(line):
    170     if not line.startswith(b'#!'):
    171         return line
    172     if b"python" not in line:
    173         return line
    174     return b'#! ' + new_interpreter + b'\n'
    175 
    176 if __name__ == '__main__':
    177     main()
    178